Fire-retardant polyolefin compositions

ABSTRACT

Flame retardants for polyolefins comprising a mixture of (a) 220 percent of brominated organic compounds and (b) 2-9 percent antimony trioxide by weight based on the polyolefin, the brominated organic compounds containing aliphatically as well as aromatically bound bromine atoms in the same molecule, such as Beta -bromoethyl-4-bromobenzene.

United States Patent 1 Kopetz et al.

1 1 FIRE-RETARDANT POLYOLEFIN COMPOSITIONS [75] Inventors: Kurt Kopetz; Willi Ziegenbein;

Anton Schick, all of Marl, Germany 173] Assignee: Chemische Werke Huels Aktiengesellschaft, Marl, Germany [22] Filed: July 27, I973 [2]] Appl. No.: 383,272

Related US. Application Data [63] Continuation of Ser. No. 92,943, Nov. 25, 1970,

abandoned, and a continuation-in-part of Ser. No. 677.062, Oct. 23, 1967, abandoned.

130] Foreign Application Priority Data Oct, 28, 1966 Germany 40545 [52] US. Cl.260/45.75 B; 260/4585 R; 260/457 R; 260/4595 G; 260/479 5; 260/612 R; 260/890 [51] Int. Cl. C08f 45/58 [58] Field of Search. 260/457 R, 45.85 R, 45.95 G, 260/479 S, 612 R [56] References Cited UNITED STATES PATENTS 2,676,946 4/1954 McCurdy 260/4575 [451 May 13, 1975 3,075,944 1/1963 Wick et a1. 260/4575 3,210,315 10/1965 Blackburn et a1. 260/4585 3,275,578 9/1966 Pedjac 260/25 3,372,141 3/1968 Dickerson et a1... 260/4595 3,419,518 12/1968 Mahling 260/4575 3,658,634 4/1972 Yanagi et a1 260/457 3,660,351 5/1972 Schmidt ct al.. 260/4585 3,728,304 4/1973 Hirao 260/4575 3,808,171 4/1974 Mohajer 260/4575 3,830,766 8/1974 Praetzel et al. 260/4575 Primary Examiner-V. P. Hoke Attorney, Agent, or Firm-Millen, Raptes & White [57] ABSTRACT Flame retardants for polyolefins comprising a mixture of (a) 2-20 percent of brominated organic compounds and (b) 2-9 percent antimony trioxide by weight based on the polyolefin, the brominated organic compounds containing aliphatically as well as aromatically bound bromine atoms in the same molecule, such as B-bromoethy1-4-bromobenzene.

6 Claims, No Drawings FlRE-RETARDANT POLYOLEFIN COMPOSITIONS CROSS REFERENCE TO RELATED APPLICATION This application is a continuation-in-part of application Ser. No. 677,062, filed Oct. 23, 1967, and claims the same priority of German Application C 40,545 Ive/39 b, filed Oct. 28, 1966. This is a continuation of application Ser. No. 92,943, filed Nov. 25, 1970 now abandoned and 677,062, filed Oct. 23, 1967 now abandoned.

BACKGROUND OF THE INVENTION This invention relates to fire-retardant compositions, and in particular to such compositions based on a mixture of(a) a brominated organic compound and (b) antimony trioxide, said mixture being particularly useful for imparting noncombustibility to polyolefins.

Because of their combustion properties, ordinary polyolefins, such as polyethylene, polypropylene, polyisobutylene, etc., cannot be universally employed in the construction and other fields wherein strict underwriters' standards prevail. As a consequence thereof, several flame retardants as well as combustion tests have been proposed to attempt to remove the inadequacy of polyolefins.

With respect to combustion tests, rectangular plateshaped materials are tested (1 for flameproof properties and (2) for self-extinguishing together with flammability properties. Such tests are intended to reflect actual fire conditions, and are conducted according to two methods:

17 DIN (German Industry Standard) 4102, Sheet 1 Four plates of 1,000 X 190 X 3 mm clamped in a vertical position, and at right angles to each other to resemble the shape of a stack having a square cross section (190 X 190 mm) are hung in a vertical kiln. Air is supplied from below through a perforated bottom. The flames of about 250 300 mm in height are produced by an annular burner having 36 nozzle openings, the flames impinging upon the interior sides of the plates. For a rating of flame-proof, the fire must be selfextinguishing substantially at once after 11 minutes of flame treatment. In addition, at least percent of the plate area must be uneffected.

2. Test according to ASTM Designation D 635 56 T.

A test sample 127 X 12.7 X 3 mm is tightly clamped and then bent to an angle of 45 of the horizontal axis. A Bunsen burner (diameter about 5 mm) is used to shoot flames of a height of about 12 13 mm so that the tip of the flame reaches the end of the test sample. If after a flame time of 2 X 30 seconds, the sample does not burn any further, the classification is nonburning by this test". If the material exhibits afterburning, but without exceeding the 4 inch mark, such material is designated as self-extinguishing by this test". If the material continues burning, then it is classified as burning by this test".

In the DIN test, combustion conditions occur corresponding to a raging fire, i.e., very high temperatures fortified by the chimney configuration and heat ofcombustion of the test samples. Under such conditions, there can be used only those additives effective at relatively high temperatures.

In contrast, in the ASTM test method, a relatively small flame is employed; likewise, the mass and thus the energy capacity of the test samples is also small.

Under such conditions, it is possible that some additives having a relatively high temperature decomposition range, cannot become sufficiently effective. This is so because the combustion temperature of the plastic test sample is below the temperature at which said additives are most useful.

With respect to already known fire-retardant compositions, chlorinated paraffins in combination with antimony trioxide has been suggested for polyolefins, (Hans Vogel, Flammfestmachen von Kunststoffen [Making Synthetic Materials Flameproof], page 46, l-Iuthig Publishers). However, with such additives it is impossible to obtain polyolefins having satisfactory flame-proof properties, unless the additives are added in comparatively great amounts (over 20 percent), and such great amounts result in unacceptable mechanical properties of the final product. In addition, perhaps the greatest disadvantage of the chlorinated paraffins is that hydrogen chloride splits off at relatively low temperatures, causing corrosion of the processing machines and molds. Ordinarily, stabilizers can be added to prevent HCl liberation, but with such high proportions of chlorinated paraffins in the mixture, even the addition of very effective acid acceptors does not solve the problem.

With respect to another type of fire-retardant, aliphatic bromine compounds, already suggested for use with polystyrene (DASs [German Published Applications] 1,090,851 and 1,090,852) cannot be employed in polyolefins for the following reasons:

a. the decomposition temperatures of aliphatic bromine compounds commence far below the processing temperatures necessary for the polyoleflns; and

b. this class of compounds exhibits, in polyolefins, little or no fire-retardant effectiveness.

On the other hand, nuclear-brominated aromatic compounds, as described, for example, in German Patents 1,103,020; 1,123,823; 1,127,582; and 1,135,653 are generally effective and those difficulties associated with the use of chlorinated paraffins are avoided. In particular, the nuclear-brominated aromatic compounds can satisfy the flammability requirements of the DIN-4102 test in contradistinction to aliphatic chlorine compounds which are completely ineffective under the same conditions because of their low decomposition temperatures, and the inability of stabilizers to make any significant change in this over-all picture. It is to be noted, however, that the nuclear-brominated aromatic compounds, per se, are unsatisfactory when used in the ASTM test.

Thus, to provide an additive effective under all combustion conditions occurring in practice, i.e., satisfying both test methods to the same degree, there was proposed a combination of nuclear-brominated aromatic compounds with chlorinated paraffins, in accordance with German Patent Application C 30, 334 Ive/39b. Although these mixtures were satisfactory fire retardants, very close and accurate temperature control must be maintained during the processing step to avoid HCl liberation. This requirement that the process must be monitored to a certain extent is a drawback which detracts from the industrial acceptance of such mixtures.

SUMMARY OF THE INVENTION An object of this invention is to provide novel chemical compositions.

Another object is to provide fire-retardant compositions which on the one hand satisfy combustion conditions, and on the other hand do not necessitate the use of temperature-monitoring during the processing steps.

Upon further study of the specifications and claims, other objects and advantages of the present invention will become apparent.

To attain the objects of this invention the material to be fireproofed is provided with (a) 2-20 percent by weight of a compound containing, in the same molecule, aromatically bound bromine, as well as aliphatically bound bromine, and (b) 2-9 percent by weight of antimony trioxide, based on said material, respectively.

DETAILED DISCUSSION OF THE INVENTION This invention is particularly applicable to polyolefins, for example, polyethylenes, polypropylenes, polybutenes, and higher polyolefins, i.e., polymers consisting essentially of carbon and hydrogen, with polydiole fins being included, cg, polyisoprene, polybutadiene, and higher homologs. On the other hand, the combination of antimony trioxide and the organic bromine compound will impart fire-retardant properties to all normally combustible organic materials, and will, no doubt, be especially useful for materials not as yet even invented, but which have relatively high processing temperatures as the polyolefins.

Suitable brominated compounds containing aromati cally as well as aliphatically bound bromine in the mol ecule, are:

a mixed aromatic-aliphatic ethers wherein the nucleus as well as the aliphatic chain contain bromine, and wherein the bromine content is between 30 and 85 percent, preferably between 50 and 80 percent, and wherein the brominated aliphatic chain is open, that means, no brominated aliphatic chain is located between two nucleus, but only attached to one nucleus.

Preferred embodiments include, but are not limited 2,4,6-tribromophenyl-B,y-dibromobutylether;

2,4,b-tribromophenyl-B,'y-dibromopropylether;

2,4,-tribromophenyl-afi-dibromoethylether; 2,2'-bis[4(B,'y-dibromopropoxy)-3,5-

dibromophenyll-propane; 2,2'-bis-[4(B,'y-dibrorr1obutoxy)-3,S-

dibromophenyll-propane; 2.2'bis-[4(ct,B-dibromoethoxy)3,5-

dibromophenyll-methane; the second listed compound being particularly effective with polypropylene, and the fourth listed compound being effective with polybutene;

b. mixed aromatic-aliphatic esters wherein the nucleus as well as the aliphatic chain contain bromine. and the bromine content is between 30 and 85 percent. preferably between 50 and 80 percent, particularly those esters produced from a hydroxyl'containing aro matic compound of about 6-l2 carbon atoms and an aliphatic monocarboxylic acid of 29 carbon atoms.

2,4,o-tribromophenyl-B:y-dibromobutyric acid ester:

afi'dibromobutyric acid-2.4,o-tribromophenyl ester;

2,2'-bis[4-(fiydihromobutyric acid ester)-3,5-

dibromophenyll-propane;

2,2-bisl(a4afi-dibromopropionic acid estcrj-3,5-

dibromophenyll-ethane;

c. alkyl aromatic compounds wherein the nucleus as well as the aliphatic chain contain bromine, and the bromine content is between 30 and 85 percent, prefer ably between 50 and 80 percent, and wherein the brominated aliphatic chain is open", that means, no bro minated aliphatic chain is located between two nucleus, but only attached to one nucleus.

The preferred embodiments include, but are not limited to: a,B-dibromoethyl-2,4,o-tribromobenzene, [Ly-dibromopropyl-tribromohenzene, a-bromotribromotoluene, ot-bromoethyl-tribrom0benzene, and 2,2'-bis[4'(B,'y-dibrombutane)-3,5-dibromphenyl}- propane.

in general, the aliphatic portion of the molecule contains l to [3, preferably 2 to 9 carbon atoms, and the aryl portion 6 to 12 carbon atoms.

The mixed ethers and esters which are brominated aliphatically as well as aromatically are obtained by brominating. for example, unsaturated ethers or esters produced by alkylation, vinylation, or allylation, or by reacting the brominated phenols with acid chlorides, in a conventional manner.

The brominated alkyl aromatics are obtained by com ventionally alkylating, for example, according to Frie delCrafts, an aromatic compound, such as benzene, with alkyl halides, alcohols or olefines, and then brominating the resultant hydrocarbon at elevated tempera ture under the effect of actinic light first in the side chain, and thereafter at a lower temperature in the presence of a catalyst in the nucleus, this sequence being also reversible. A further possibility resides in alkylating the aromatic compound with alkenyl halides, and then reacting the unsaturated side chain with bromine or hydrogen bromide at a lower temperature, followed by the catalytic nuclear bromination.

Specific alkyl aromatic compounds are obtained by brominating, for example, previously brominated styrenes, such as 2,4,64ribromostyrene or 4- bromostyrene in the vinyl chain,

it is preferred to distribute the bromine content in approximately equal portions, e.g., ll) to 70 percent, especially 20 to 60 percent to the nucleus and the aliphatic group. However, some fire retardancy is obtained if at least one bromine atom is bound to one of these groups. Since the ethers and esters. if desired, can be produced by the condensation of two prebrominated, pure and specific individual components, it is possible to employ chemically specifically defined compounds having a known and unitary bromine distribution. In contrast thereto, in the case of brominated alkyl aromatics, if produced by brominating a brominefrce alkyl or alkenyl aromatic compound, there will be produced mostly mixtures of compounds brominated to different degrees and at different places.

Important brominatcd compounds of this invention include. but are not limited to:

2,4,o-Tribromophenyl-B-y-dibromobutylether;

2,4,6-Tribromophcnyl-a,,8-dibromoethylether; 2,2Bisl4(,6,ydibromopropoxy )3,5

dibrornophcnyl]-propane: 2,2'-Bisl4lBytlibromobutoxy) 3,5-

dibromophenyl l'propanc', 2,4,o lribromophenylfiytlibromobutyric acid ester;

afi-Dibromobutyric acid-2,4,o-tribromophcnylestcr;

2,2-Bisi4-([3,y-dibromobutyric acid ester)-3,5

dibromophenyll-propane, a,BDibromocthyl-2.4,o-tribromobenzene; a,7--dibromopropyl-2,4.b-tribromobcnzene.

The antimony trioxide is employed in amounts of from 2 to 8, preferably 2 to 5 percent, and the brominated compound is 2-20 percent, preferably 2 to l0, by weight. based on the polyolefin.

The individual components are admixed to the base material, eg. polyolefins in optional succession, or simultaneously, and blended in a conventional manner with other additives such as fillers, pigments, stabilizers, etc. The thus-obtained mixtures are shaped by conventional methods, e.g., molding.

Without further elaboration, it is believed that one skilled in the art can, using the preceding description, utilize the present invention to its fullest extent. The following preferred specific embodiments are, there- COMPARATIVE EXAMPLES 6-l 3 The following compositions were subjected to the same tests according to DIN 4lO2, and according to ASTM D 635 T 56:

a. 100 parts by weight of polypropylene 5 parts by weight of bromine compound 2 parts by weight of antimony trioxide b. 100 parts by weight of polybutene-l 5 parts by weight of bromine compound 2 parts by weight of antimony trioxide The bromine compounds were:

I. 2,4,6-Tribomophenyl-a,y-dibromopropyl ether fore, to be construed as merely illustrative, and not limu n itative of the remainder of the specification and claims l l in any way whatsoever, Table l, as follows, sets forth T i Q H self-explanatory examples: Br H Br Br TABLE 1 Examples Recipe Plate Test Test According Remarks DlN 4102 to ASTM D 635 I 100 parts by weight of polypropylene passed Nonburning Drippings of material (molecular weight ca. 300,000) do not continue to 6 parts by weight of 2,4,otribromoburn on th fl r phcnyluJi-dibromocthylether 4 parts by weight of antimony trioxide 2 100 parts by weight of polypropylene passcd. Nonburning Drippings of material (Molecular weight ca. 300,000) do not continu t S parts by weight of 2.2'-bis-[fi.7 burn on the floor dibromo-butyric acid ester-3,5- dibromophenyll-propanc 5 parts by weight of antimony trioxide 3 I00 parts by weight of polybutcne-( l passed Nonburning Drippings of material (molecular weight ca. 2,000,000) do not continue to 5 parts by weight of 2.2'-bis-I4-(B,7 burn on the floor dibromo-propoxy)-3.Sdibromophcnyllpropane 4 parts by weight of antimony trioxide 4 I00 parts by weight of polybutcnc( l passed Nonburning Drippings of material (Molccular weight ca. 2,000,000) do not continue to 7 parts by weight of 2,4,h-tribromophcnyl burn on the floor fi-y-dihromobutyric acid ester 4 parts by weight of antimony trioxide 5 I00 parts by weight of polyethylene passed Nonburning Drippings of material (molecular weight ca. 50,000) do not continue to 8 parts by weight of 2,2-bisl4(B,-yburn on the floor dibromo-butyric acid ester l-3,5- dibrornophcn ll-propane 5 parts by wcig t of antimony trioxide The particular advantages achieved by the present g gtgi l 4. fg dib .3 5-

invention reside not only in obtaining less temperaturesensitive mixtures, which can be thermoplastically shaped without any special precautions under the convcntional processing conditions, e.g. temperatures of 200 to 240 C; but also the total amount of fireretardant additives, as compared to prior practice, can be lowered, obtaining the identical effect. Thus, with additives totalling even below 10 percent of the entire amount of the mixture, an excellent flameproof effect can be attained, and no discolorations occur in the mixtures mentioned in the examples, even at a processing temperature of 240 C.

The preceding examples can be repeated with similar success by substituting the generically and specifically described reactants and operating conditions of this invention for those used in the preceding examples.

dibromophenyll-propane Br CH Br 1 l I l l I "'i'fii' t FF" Br Br It Br 3 a ll Br Br III l,4-Bis-2,4,6-tribromophenoxy-2,3- dibromobutane Br Br r Br OCll CH CH--Cll O -Br Br Br IV. Bis-2,4,6-tribromophenyl ester of 2,3-

dibromosuccinic acid Br B Whereas l and II are compounds employed in accordance with this invention, compounds III, IV and V are compounds which could be derived from DAS l,l 35,653 The results are self-explanatory and are set forth in Table ll, as follows:

TABLE II wherein R is H or CH and R is dibromoethyl, dibromopropyl or dibromobutyl.

2. A composition as defined by claim 1, wherein said 5 compound is 2,2 -bis[ 4( B,'y-dibromopr0poxy )-3,5-

dibromophenyl ]-propane;

2,2-bis-[4(B,'y-dibrom0butoxy )-3 ,5

dibromophenyll-propane; or

-bis- [4 a,B-dibromoethoxy)-3 ,5 -dibromophenyl] methane.

Test on the Plate Examples Recipe According to DIN 4lU2 Test According to ASTM D 635-T S6 Remarks Dripped-down material does not continue burning on the floor [ground] Dripped-down material continues burning on floor do.

Dripped-down material does not continue burning on the floor dot Dripped-down material continues burning on floor do.

From the foregoing description, one skilled in the art can easily ascertain the essential characteristics of this invention, and without departing from the spirit and scope thereof, can make various changes and modifications of the invention to adapt it to various usages and conditions What is claimed is:

l. A flame-resistant polyolefin composition comprising on a weight basis [00 parts of a polyolefin, 2-9 parts antimony oxide, and 220 parts of Br Br Br Br 3. A composition as defined by claim 1 wherein said organic compound is 2,2'-bis[4-(B,ydibromopropoxy)-3,5-dibromophenyl]-propane.

4. A flame-resistant composition as defined by Claim 1 wherein the polyolefin is polypropylene.

5. A flame-resistant composition as defined by Claim 1, wherein the polyolefin is polybutene.

6. A flame-resistant polyolefin composition comprising on a weight basis lOO parts of a polyolefin, 2-9 parts antimony oxide, and 2-20 parts of a compound selected from the group consisting of:

ester)-3,5-

2,2'-bis-[4-(B,'y-dibr0mobutyric acid dibromophenyH-propane; and

2,2-bis[4-(afi-dibromopropionic acid ester)-3,5-

dibromophenyH-ethane 

1. A FLAME-RESISTANT POLYOLEFIN COMPOSITION COMPRISING ON A WEIGHT BASIS 100 PARTS OF A POLYOLEFIN, 2-9 PARTS ANTIMONY OCIDE, AND 2-20 PARTS OF
 2. A composition as defined by claim 1, wherein said compound is 2,2''-bis(4( Beta , gamma -dibromopropoxy)-3,5-dibromophenyl)-propane; 2,2''-bis-( 4( Beta , gamma -dibromobutoxy)-3,5-dibromophenyl)-propane; or -bis-(4( Alpha , Beta -dibromoethoxy)-3,5-dibromophenyl)-methane.
 3. A composition as defined by claim 1 wherein said organic compound is 2,2''-bis(4-( Beta , gamma -dibromopropoxy)-3,5-dibromophenyl)-propane.
 4. A flame-resistant composition as defined by Claim 1 wherein the polyolefin is polypropylene.
 5. A flame-resistant composition as defined by Claim 1, wherein the polyolefin is polybutene.
 6. A FLAME-RESISTANT POLYOLEFIN COMPOSITION COMPRISING ON A WEIGHT BASIS 100 PARTS OF A POLYOLEFIN, 2-9 PARTS ANTIMONY OXIDE, AND 2-20 PARTS OF A COMPOUND SELECTED FROM THE GROUP CONSISTING OF: 2,2''-BIS-(4-(B,Y-DIBROMOBUTYYRIC ACID ESTER)-3,5DIBROMOPHENYL!-PROPANE; AND 2,2''-BIS 4-(A,B-DIBROMOPROPIONIC ACID ESTER)-3,5DIBROMOPHENYL!-ETHANE. 